Protective relay for series releases



W. H. PETERSN PROTECTIVE RELAY FOR SERIES RELEASES Jan. 3, 1923.

Filed Dec. 11, 1925 Patented Jan. 3, 1928.

UNITED STATES PATENT oFFicE.

WILHELM HENNING PETERSN, 0F LUDVIKA, SWEDEN, ASSIGNOR TO ALLMANNA. SVENSKA ELEKTRISKA AKTEBOLAGET. OF VilrSTERAS, SWEDEN, ACORPOB-ATION OF SWEDEN.

PROTECTIVE RELAY FOR SERES RELEASES.

Application filed December 11, 1925, Serial No. 74,706, and in Sweden November 4, 1924.

Relays of the kind which act to close a circuit through the release coil of a circuitbreaker for instance in the case of an overload, are often so arranged, that the source of current acting on the relay (for instance a current transformer) also energizes the release coil so that no separate source of current is necessary for this purpose. This arrangement-so-called series releaseis generally carried out in such manner that the relay is made to break a contact normally short-circuiting the release coil.

Vhen the relay serves for protection against overload current in a section of a transmission system, it is likely to occur, that on a powerful short-circuit in the system, the current traversing the relay becomes too strong for being controlled by its own contacts. For such cases it has been proposed to use an intermediary relay which 1s energized by only a branch of the current, said branch being closed for the releasing operation, While the main portion of the current normally traverses a resistance. The latter may also serve as a blow-out coil for the contacts of the intermediary relay which normally short-circuit the releasing coil.

The present invention is based upon the last-mentioned principle and has for its main object to utilize the aforesaid parallel resistance in a still more ellicient degree. According to the invention, the resistance, Which retains the shape of a coil, is so arranged that its ampereturns also will act on the armature of the intermediary relay on the occasion of a release, while they in the same time may be utilized for blowing out the arc. In a preferred form of the invention, the intermediary relay is provided with a three-legged iron core on which the coil controlled by the primary relay is situated on one of the outer legs while the shunt coil is placed on the middle leg.

In the accompanying drawing, the aforesaid preferred form of the invention is illustrated. Fig. 1 shows a diagram of connections and Figs. 2 and 3 the mechanical design of the intermediary relay in two views perpendicular to one another.

Referring to Fig. 1, 1 is the primary and 2 the secondary winding of a current transformer, 3 the coil and 4 the contacts of the primary relay. The latter may be of any appropriate type,for instance with or withn out time lag, and, in the former case, with a time lag dependent or not upon the amount of current or voltage. The current path from the secondary winding 2 is divided into two branches after passing through the coil 3, one of said branches passing directly through a coil 5 on the intermediary relay, while the other passes over thecontracts et to another coil 6 of the said intermediary relay. The lirst coil (shunt coil) is placed on the middle leg, the second on one outer leg of the three-legged iron core 7. Beyond these coils the two current paths are united in one, but this is divided again, one branch passing through the release coil 8 of the circuit breaker and the other over the contacts 9 of the intermediary relay, before the current returns to the transformer.

Referring to Figs. 2 and 3, the armature 10 of the intermediary relay is pivoted in the middle leg of its iron core and provided with a spring 11 or the like which normally pulls it towards the non-wound outer leg, a stop 12 (preferably adjustable) normally preventing direct contact between the armature and the said outer leg. The contact S) actuated by the armature yis preferably not rigidly connected thereto, but pivoted and actuated by means of a projection 15 mov able to a certain extent independently of the armature, whereby the breaking will be more rapid. The Contact 9 is provided with a special springle pressing it against the corresponding fixed contact. A pair of shields 15, 16 embracing the Contact point constitute a shunt of the magnetic field which acts extinguishing upon the arc.

The general manner of operation of vthe device is as follows: Normally the current flows only through the coil 3 of the primary relay and the coil 5 on the middle leg of the intermediary relay and back to the transformer over the contacts 9. Hereby a magnetic field is produced in the intermediary relay which is divided between the two outer legs substantially in inverse proportion to the width of the two air gaps. By suitably adjusting the stop 12 the attraction of the non-wound leg can be made to dominate a little over that of the leg carrying the coil 6. When the current sinks to a low value or to zero, the spring 11, which may be rather cuit through the coil 6, the attraction et the,

magnet leg carrying that coil Will be predominant. As soon as the armature beginsV to tip over as a consequence hereof, the attraction ofV the last-mentioned' leg increases very rapidly, the two coils and 6 now cooperating to this effect. The arinature hereby acquires a considerable speed before the projection 13 strikes the movable contact, so as to he able to overcome the tension :of the strong spring 14 and break the circuit. By the aforesaid blow-out field the arc is rapidly extinguished even at the heaviest occurring short-circuit. I the the interruption at 9 the release coil 8 is energized and the release eiiected.

I claim as my invention:A

1. ln secondary electric relays, an iron core having three legs substantially in one plane, energizing coils on the middle and one uter leg of said iron core, said coils being permanently connected together' at one end and adapted to be temporarily connected in parallel, an armature pivoted in said middle leg and capable or" being Y attracted alternatively by either of saidpouter legs, the attraction of the leg having no coil being normally preponderant, a stop preventing the immediate contact between said armature and said non-Wound leg, and contact means actuated by said armature when attracted by theother outer1 leg. l

2. In secondary electromagnetic relays an iron core having three legs substantially in one plane, an armatnre pivoted in the middle one of said legs and `capable of being alternatively attracted by either of the outer legs, a. coil, adapted to be permanently in circuit, mounted on said middle leg, a coil, adapted to be connected temporarily in eircuit, mounted on'one of said outer legs, a

contact pivoted to said armature, aprojection on said armature capable ot' acting on said contact, and a spring normally pressing said Contact against a iixed Contact. Y

3. ln electric relays, an iron core, energizing coils on'tivo legs of sai-d iron core, said coils being connected together at one end and vadapted to cooperate, whenA connected in parallel, to attract an armatnre'to complete the magneticcircuit thro-ugh said legs, Y armature, v

contact means actuated by said? and a magnetic iren path shuntinga portion of the aforesaid magnetic circuit and having an air gap containing said contact means. Y

ln testimony whereof l have signed my name to this specification. i

ILHLM HENNING PETERSN. 

